The present invention generally relates to semiconductor fabrication and, more particularly, to systems and methods for managing a semiconductor fabrication facility using wafer lot attributes and cassette attributes.
Semiconductor manufactures compete in a highly competitive and capital-intensive industry. A state-of-the-art semiconductor fabrication plant typically includes hundreds of different fabrication tools and can cost $1 billion or more. New plants can also become obsolete relatively quickly as the dimensions of semiconductor devices decrease.
A conventional semiconductor fabrication plant typically includes multiple fabrication areas or bays interconnected by a path, such as a conveyor belt. Each bay generally includes the requisite fabrication tools (interconnected by a subpath) to process semiconductor wafers for a particular purpose, such as photolithography, chemical-mechanical polishing, or chemical vapor deposition, for example. Material stockers or stocking tools generally lie about the plant and store semiconductor wafers waiting to be processed. The wafers are typically stored in containers, such as cassettes each of which can hold up to 25 wafers. Each material stocker typically services two or more bays and can hold hundreds of cassettes. While not shown, the semiconductor fabrication plant, including the bays, material stockers and the interconnecting path, typically operates under control of a distributed computer system running a factory management program, such as WorkStream Open sold by Consilium, Inc.
A typical semiconductor fabrication plant, such as the one described above, handles the processing of thousands of wafers at any given time. The wafers are typically divided into lots which undergo different processing sequences. In some instances, as a result of the different process sequences running simultaneously, certain wafer lots may become incompatible with others. For example, wafer lots exposed to a material, such as copper or cobalt, are typically desired to be separated from other lots within the plant. Conventional semiconductor fabrication facilities handle these xe2x80x9ccontaminatedxe2x80x9d wafers by physical separation. That is, physical barriers are created between areas in the facility and cassettes are bound to a designated area so as to avoid cross-contamination. When a wafer lot moves from one area to a new, physically separated area, a cassette from the new area receives the lot for processing in the new area. In this manner, conventional fabrication plants strive to separate contaminated wafer lots from lots incompatible therewith.
To generate higher revenues, semiconductor manufactures continually seek to increase to the throughput and yield of semiconductor wafers and find systems and methodologies which increase either of these parameters to be highly desirable.
The present invention generally provides techniques for managing automated material handling systems, such as semiconductor fabrication facilities, using material attributes and cassette attributes. These techniques may, for example, significantly increase the throughput of material through these systems.
A process and system for managing a semiconductor fabrication facility having multiple wafer lots and multiple cassettes for holding the wafer lots, in accordance with one embodiment of the invention, includes setting one or more lot attributes for each wafer lot, setting one or more cassette attributes for each cassette, and selecting a particular cassette for holding a particular wafer lot based on the one or more wafer lot attributes of the particular wafer lot and the one or more cassette attributes of the particular cassette. The wafer lot and cassette attributes may, for example, include an attribute identifying a position in a fabrication sequence and one or more attributes indicative of one or more contaminants. By selecting cassettes in this manner, wafer lots and cassettes may, for example, be classified or logically zoned.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures in the detailed description which follow more particularly exemplify these embodiments.